Here is another short list, a list of pet peeves I have collected on Stack Overflow and related websites:

SI units

To avoid ambiguities, there is a general consensus on how to format physical units. Please try to follow them, it helps the flow when reading, and it helps when trying to understand exactly what you are talking about. The official guidelines are offered in chapter 5 of the SI brochure, but there is a summary with a couple of examples on Wikipedia.

A particular problem is the space between the value and the unit, for example: 12 V, not 12V. A common hack is to use the non-breaking space, &nbsp;, to prevent the browser wrapping the line between the value and the unit. The problem with &nbsp; is that it is often interpreted as a fixed width space, meaning that it will not render as the same width as a normal space, but wider. Unicode has solved this problem by introducing the NARROW NO-BREAK SPACE symbol, &#8239;.

My recommendation is that you use &#8239; to format SI units. This difference may or may not be visible in your browser:

12 V (normal space)

12 V (&nbsp;)

12 V (&#8239;)

"I'm in Europe."

This means nothing. Nothing at all to anyone trying to help you with a question you might have. Either write your country, or just leave it out - There's a world of difference (literally) between Turkey, Switzerland, Portugal, Romania, United Kingdom and Iceland. Different laws, different business structures, different traditions, different standards. The same goes for Asia.

Leaving out your country means that you will not get help with questions such as: